1/24th shutter in 60P mode - physically impossible.

B

broughtonfilm

Well-known member
Sorry if this has been discussed but why does the camera allow to dial 1/24th of the second shutter speed when shooting in 60p (VFR on) ? It is physically impossible as the longest exposure time can be 1/60th of a second when shooting at 60p ( 360 degree shutter). Changing it from 1/24th to 1/60th does not change exposure therefore I assume that 1/24th is in fact 1/60th (longest possible exposure at 60p).

Also, it is inconsistent that when shooting at 24p "shutter off" means in fact 180 degree shutter (1/48th of a sec., like in any other video camera) and in 60p "shutter off" means 360 degree shutter (1/60th of a second).
 
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As I understand it "shutter off" means 1/60th of a second. Always.

It is better to shoot at 180 degrees then the shutter is adjusted for you when you change frame rate.

As I understand it IF you set a shutter speed that is physically impossible for your frame rate, that is too slow, the frame rate adjusts to the fastest VFR possible, I would also guess at a 360 degree shutter.
 
Steve Kahn said:
As I understand it "shutter off" means 1/60th of a second. Always.
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If "shutter off" was always 1/60th of a second as you suggest then it would also be 1/60th of a sec. with "shutter off" at 24P. That is not the case as the exposure does not change when you switch from "shutter off" to 180 degree at 24p setting. It is a standard in most video cameras that "shutter off" as a default equals 180 degree (and therefore shutter speed is a half of the frame rate, i.e . in 24P it is 1/48th ).

With AF100 it is kind of inconsistent. Maybe there is some reason for it which I don't understand, that's why I am posting the question.

Steve Kahn said:
As I understand it IF you set a shutter speed that is physically impossible for your frame rate, that is too slow, the frame rate adjusts to the fastest VFR possible, I would also guess at a 360 degree shutter.
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I find it to be more of a confusion than camera's intelligent help: if the given shutter speed is not possible then the camera should not allow it to be dialed in (even thou it actually finds the slowest possible one instead). That leads to confusion - camera tells you that your shutter speed is 1/24th while it actually is 1/60th in case of 60p.
 
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This is partially answered on pg 220 of Barry's book:

'With SHUTTER OFF the camera selects a default shutter speed of 1/60 for 24P or 30P' (in NTSC).

1/60 is used to eliminate light/computer monitor flicker.
 
I thought "no shutter" implied a shutter speed native to the framerate, IE 180º shutter. In this case, 1/48 for 24fps. I'll check it out tomorrow.
 
indeed very confusing issues.

Taylor Rudd said:
I thought "no shutter" implied a shutter speed native to the framerate, IE 180º shutter. In this case, 1/48 for 24fps. I'll check it out tomorrow.
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That's exactly what I thought until I read the book again earlier this week to fine tune myself for a shoot.
 
Steve Kahn said:
indeed very confusing issues.



That's exactly what I thought until I read the book again earlier this week to fine tune myself for a shoot.
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Yes it is confusing , on page 15 of AF100 manual (advanced) available here it says that this shutter speed is actually 1/50th of a sec. Check it out:
Screen shot 2011-02-24 at 11.10.24 PM.jpg
 
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Barry_Green said:
It is 1/60 in 60i/60p and 1/50 for 24/25/30/50p and 50i.
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Thanks for the info. Is the shutter speed for 24P with 180 degree shutter also a 1/50th of a sec. or is it a true 1/48th of a sec?

I was always under impression that "shutter off" setting defaulted to 180 degree shutter and therefore was actually the same setting as a shutter set to "on" at 180 degree. I am noticing now that HVX200's "shutter off" shutter speed is also a 1/50th of a second.
 
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Barry_Green said:
In the Panasonic AG series, "shutter off" really meNs "default shutter speed."

180 degrees at 24p = 1/48.
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There is a lot of confusion about "shutter off" default shutter speed online , I guess because it means something different depending on camera model, class and its make. I think 1/50th as a default "shutter off" speed in NTSC mode is a bit unexpected but at the same time very useful.

As far as the first part of my original question (1/24th in 60P mode), I think it is just a small firmware quirk that AF100 allows dialing in impossible shutter speed? What is your take on that , Barry?
 
The af100 allows slow shutter speeds which results in a process called "frame accumulation." It causes buffeting until the exposure is complete, and duplicated frames in the data stream. It is no different from how 60i cameras have been offering slow shutter speeds for at least the last decade. You cannot have a shutter speed longerthan your frame rate without causing frame duplication.

I am on a plane so can't check but I think the slow shutter is only an option in "video cam" mode which makes sense. In film cam mode you can't go below 1/24.
 
Barry_Green said:
The af100 allows slow shutter speeds which results in a process called "frame accumulation." It causes buffeting until the exposure is complete, and duplicated frames in the data stream. It is no different from how 60i cameras have been offering slow shutter speeds for at least the last decade. You cannot have a shutter speed longerthan your frame rate without causing frame duplication.

I am on a plane so can't check but I think the slow shutter is only an option in "video cam" mode which makes sense. In film cam mode you can't go below 1/24.
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You can dial in 1/24th in 60P in film mode, something that is obviously impossible as the longest shutter speed in 60P can be 1/60th (with 360 degree shutter). Motion does not look like that known in "frame accumulation". Camera probably defaults to the longest possible exposure time in 60P mode (1/60th) but for some reason displays it as 1/24th. Have a safe flight.
 
also, frame accumulation looks like crap.

so if you need 1/24 or 1/12 or 1/3, shoot 24fps, 12fps, or 3fps.


edit additional info: also think of it like this

1sec = apple pie.

60 people want apple pie.
each person has to get the same size slice.
the largest a slice can be is 1/60 of the pie.
thus it is impossible to give 60 people a slice that is 1/24 of the pie.
 
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zijital said:
also, frame accumulation looks like crap.

so if you need 1/24 or 1/12 or 1/3, shoot 24fps, 12fps, or 3fps.


edit additional info: also think of it like this

1sec = apple pie.

60 people want apple pie.
each person has to get the same size slice.
the largest a slice can be is 1/60 of the pie.
thus it is impossible to give 60 people a slice that is 1/24 of the pie.
Click to expand...

Well... I think I understand it. It is worth reading entire thread before responding or at least the first question. Thanks for an apple pie anyway. ;)
 
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